The driver said the bus was taking 35 tourists from Krabi to a Lomprayah pier in Don Sak, where they were to board a ferry to Koh Samui.

Pol Col Sutthi said the driver and his assistant have been charged with having narcotic substances in their bodies, and their cases will be forwarded to state prosecutors in the province, the Bangkok Post reported.

They could face fines of up to 40,000 baht and an unspecified jail term if found guilty, according to Manop Sutthiphan, the chief of the land transport provincial office.

The transport official said Lomphayah had informed his office that both of them had been fired following the accident.